New GRACE satellite data on sea level rise from melting ice caps

Boulder
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A publication in the journal Nature by scientists at the Univ. of Colorado, has estimated that from 2003 to 2010 the world's glaciers and ice caps lost about 150 billion tons annually, causing an average annual rise of 0.4 millimeter in sea level.

The New York Times reports that the study was based on satellite measurements taken by two Gravity Recovery and Climate Experiment satellites (GRACE), a joint project of NASA and German scientists. The satellites, flying 137 miles apart, detect regional changes in the Earth’s mass and gravitational pull caused by the distribution of water and ice on the planet. It is the first satellite measurement estimating contribution of the world's melting glaciers and ice caps to global sea level rise.

The satellite measurement showed that melting ice added about 0.4 millimeters annually to the total sea level, excluding contributions from Greenland and Antarctica. Rise in sea levels from melting ice including Greenland and Antarctica was roughly 1.5 millimetres annually or about 12 millimeters, or one-half inch, from 2003 to 2010.

Between 2003 and 2010, the world's glaciers and ice cap lost about 148 billion tons or about 39 cubic miles of ice annually, excluding loss from individual glacier and ice caps on the fringes of the Greenland and Antarctic ice sheets, which, according to Daily Mail, the researchers say add about 80 billion tons per year. According to Professor Wahr of the Cooperative Institute for Research in Environmental Sciences at University of Colorado, Boulder, "The total amount of ice lost to Earth's oceans from 2003 to 2010 would cover the entire United States in about one-and-half feet of water."

Opponents of the proponents of global warming have pointed to the lower rates of loss of glaciers and ice caps returned by the GRACE measurements as evidence that the alarm being raised about global warming is unfounded. They point to the fact that satellite data revealed that the Himalayan glaciers are melting at a far slower rate than predicted by scientists. According to the data obtained from the satellites, the Himalayan glaciers are melting at a rate of 4 billion tons annually in contrast to the 50 billion tons per year predicted by scientists.

Daily Mail reports scientists had predicted that Himalayan glaciers would have melted to a fifth of current levels by 2035 and that this would lead to significant rise in seal level and drought. But the new measurements returned far less rates of loss of ice in the Himalayas.

Lewis Page of The Register, said: "It had been suggested by hard-green campaigners, and regrettably endorsed by the UN Intergovernmental Panel on Climate Change that the Himalayan glaciers might disappear by the year 2035, leading to imminent drought and starvation for billions, a claim since widely rubbished. The new GRACE readings would seem to be further confirmation of that prediction's foolishness."

But such statements miss the fact that discovery of significantly lower rates of loss than predicted do not change the fact that even at the new estimated rates, the world is losing its glaciers and ice caps at a high rate. Professor Wahr said: "The Earth is losing an incredible amount of ice to the oceans annually."

The Telegraph points to the statement by the researchers that the implications of the lower rates for projected "sea level rises by 2100AD is small: about 5cm lower than the 30cm to 1m currently estimated." According to The Telegraph, science is not a "conspiracy" but an "open process," in which conclusions are subject to revisions with improved data and information.

According to Professor John Wahr,"The results [in the Himalayas] region really were a surprise. One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and were extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, many of the high glaciers would still be too cold to lose mass, even in the presence of atmospheric warming. What is still not clear is how these rates of melt may increase and how rapidly glaciers may shrink in the coming decades. That makes it hard to project into the future."